Not up on them
But as far as I can tell, no or virtually know 3rd party app development. Locked in devices with closed up OS's that are great for email, but not for any sort of computing outside the little boxes they give you.
There are a lot of things happening with mobile foss linux, too. I'm not a foss junkie and I don't really buy the credo, but we'll see.
I have hope for android- and like I said, I still pray for Palm.
Yeti